When creating a index in Mongo shell, I got the correct exception:

`> db.case_detail.createIndex(

,

)
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 9,
"errmsg" : "exception: Btree::insert: key too large to index, failing guangdong_courts.case_detail.$案号_1 5360 { : \"（2015）佛明法民一初字第653号当事人:原告:杨瑞芳,被告:李永清\n案由:民间借贷纠纷\n开庭时间:2015-11-3 15:00\n开庭地��...\" }",
"code" : 17280,
"ok" : 0
}` ,

But when I use pymongo, I got this error:

`---------------------------------------------------------------------------
UnicodeDecodeError Traceback (most recent call last)
/mongo-python-driver/bson/_init_.py in decode_all(data, codec_options)
806 obj_end,
--> 807 codec_options))
808 position += obj_size

/mongo-python-driver/bson/_init_.py in _elements_to_dict(data, position, obj_end, opts)
343 result = opts.document_class()
--> 344 for key, value in _iterate_elements(data, position, obj_end, opts):
345 result[key] = value

/mongo-python-driver/bson/_init_.py in _iterate_elements(data, position, obj_end, opts)
336 while position < end:
--> 337 (key, value, position) = _element_to_dict(data, position, obj_end, opts)
338 yield key, value

/mongo-python-driver/bson/_init_.py in _element_to_dict(data, position, obj_end, opts)
325 obj_end, opts,
--> 326 element_name)
327 except KeyError:

/mongo-python-driver/bson/_init_.py in _get_string(data, position, obj_end, opts, dummy)
131 return _utf_8_decode(data[position:end],
--> 132 opts.unicode_decode_error_handler, True)[0], end + 1
133

UnicodeDecodeError: 'utf-8' codec can't decode bytes in position 255-256: invalid continuation byte`